Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

875
FXUS63 KLOT 111100
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
600 AM CDT Sat Apr 11 2026

.KEY MESSAGES...

- An unseasonably warm and humid pattern will arrive on Sunday
  and persist through at least the middle of the workweek,
  accompanied by periodic showers and thunderstorms, and a
  threat for severe weather Monday night through Wednesday.

&&

.DISCUSSION...
Issued at 337 AM CDT Sat Apr 11 2026

Through Tonight:

Patchy shallow fog outside of Chicago will quickly erode after
sunrise this morning. The lingering influence of seasonably
strong and expansive surface high pressure over the Great Lakes
region will result in an overall quiet daytime period. Following
a mostly sunny to partly cloudy start to the day, mid and high
level cloud cover will overspread the area and likely limit
further temperature rises. Expect highs in the mid 50s to lower
60s (locally mid 60s far southern sections) for inland areas and
only in the upper 40s to around 50F near the lake in northeast
Illinois and in far northwest Indiana due to onshore flow and
afternoon lake breeze reinforcement.

The aforementioned advancing mid and high clouds today are
associated with a series of mid-level impulses overtopping broad
mid and upper level ridging over the region. Some previously
more aggressive guidance has begun to back off with respect to
shower coverage this evening due to antecedent dry low levels.
Due to fighting dry air and a lack of robust large scale
forcing, only isolated to widely scattered light to perhaps
moderate showers may occur, primarily north of I-80. Have
focused the highest PoPs (40-50%) across far northern Illinois.
Mostly, if not entirely dry conditions are favored overnight and
as such, we may be able to scale back on low PoPs near and
north of I-80. Forecast lows will range from the mid 40s near
the lake in northeast Illinois to the mid 50s well inland. As a
stout low-level jet moves overhead in the pre-dawn hours of
Sunday, breezy southerly winds will likely result in slowly
rising temps.

Sunday through Friday:

Western and High Plains troughing will result in fairly
amplified downstream ridging through most of the upcoming week,
resulting in late spring to early summer-like temperatures.
While plenty of dry time can be expected, there will be multiple
opportunities for convection.

On Sunday, a strong warm front will surge northward as mid 990s
mb surface low pressure tracks towards the Arrowhead region of
Minnesota. If mixing is deep enough (ie. cloud cover not too
thick), robust southwesterly gradient flow may yield gusts in
excess of 40 mph, though will message peak gusts of 35-40 mph
due to uncertainty.

A subtropical impulse emanating from near the Baja California
will interact with the warm (temps in the 70s, locally ~80F
southern CWA) and humid (dew points well into the 50s to ~60F)
airmass over the region to result in increasing shower coverage.
This will particularly be the case in the afternoon near and
northwest of I-55 and area-wide Sunday evening. The synoptic
pattern would be more concerning from a severe weather threat
perspective if steeper mid-level lapse rates were anticipated.
As is, the subtropical nature of the primary forcing mechanism
will likely result in modest mid-level lapse rates, limiting
instability and equilibrium levels.

For the above reason, confidence is higher in showers than in
any thunderstorms materializing. The best chance for embedded
thunderstorms is expected to focus over the northwest 1/3 to 1/4
of the CWA from the late morning through the early to mid
afternoon until lapse rates further decline. There may then be
another window for potential widely scattered embedded storms
after midnight into early Monday. Well above normal precipitable
water values and deep moist profiles with unusually high
freezing levels could very well result in periodic downpours,
though limited thunderstorm coverage should tend to keep rates
and amounts in check.

During the upcoming workweek, the prevailing mid and upper level
pattern will tend to focus ejecting short-wave energy and
corresponding stronger large scale forcing to the north and
northwest of our area. This lowers confidence in specific
details, with more subtle impulses and/or MCVs playing a larger
role. On Monday, any lingering convection from overnight should
focus southeast and end in the morning. In the afternoon, height
rises and dry mid-level air will likely suppress renewed
convective development, with the best chance (30-40%) generally
well south of I-80. Monday should have similar to slightly
warmer highs than on Sunday.

Monday night is the first period of interest for organized
convection, and it appears rather conditional, being tied to an
MCS that *may* propagate across the upper MS Valley towards the
western Lakes. If this impulse doesn`t materialize or ends up
farther north, chances for storms and any threat for severe
weather (wind and hail) will commensurately decrease. On the
other hand, in the presence of sufficient forcing, very steep
modeled mid-level lapse rates support the level 1-2/5 severe
threat.

Tuesday and Wednesday continue to look synoptically supportive
for the SPC outlooked severe threats. However, as alluded to
earlier, unknown (at this time) mesoscale details can be expected
to modulate the relative threat into our area. Neutral height
tendencies on Tuesday afternoon and evening, but the presence
of the warm frontal boundary near or just north of the area lend
to concern for supercellular storm mode and a threat for all
severe hazards somewhere in the region. On Wednesday, large
scale forcing will uptick some, but there`s plenty of
uncertainty regarding timing of an approaching cold front. Plus
the parent surface low tracking well north and not quite as
steep mid-level lapse rates may relegate the primary severe
threat (if one materializes locally) to damaging winds. There
eventually should be a quieter period later in the workweek,
though confidence is low in specifics.

Castro

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 600 AM CDT Sat Apr 11 2026

Key aviation forecast messages:

- Lingering patchy fog early this morning in outlying areas.

- Spotty showers are possible this evening (30% chance).

- Increasing SE winds overnight becoming SW Sunday morning, with
  gusts to 30 kt likely by midday.

Shallow ground fog continues in low-lying areas outside of
Chicago, particularly in river valleys. This is expected to
erode and lift after daybreak.

Light and variable winds early this morning will return to a
prevailing east to southeast direction after daybreak increasing
to around 10 kt. High clouds increase in coverage through the
day today ahead of a disturbance approaching the region.
Associated decaying showers may then drift into the area into
this evening, though coverage may be rather limited as they
encounter a drier low-level airmass here locally and have
accordingly maintained PROB30s for -SHRA with only minor timing
refinement.

Winds then trend SSE late this evening and overnight. Speeds
also increase steadily through the night with sporadic gusts
into the lower 20 kt range possible by daybreak Sunday. There is
a narrow window for low-level wind shear concerns during the
~9-14Z timeframe as a southwesterly low-level jet strengthens
overhead (45-50 kt) prior to more efficient mixing setting up
after daybreak. Have held off on a formal LLWS mention for now
but may need to consider it with later updates. Winds then turn
SSW Sunday morning with gusts increasing to near 30 kt by mid
to late morning. Scattered showers may approach ORD and MDW by
late Sunday morning, though it appears any isolated TS should
focus northwest of the Chicago terminals.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago